Prostaglandins (PCs) play a role in a variety of physiological functions; e.g. immune responses, platelet aggregation, reproduction, respiratory function, thermoregulation. Exaggerated production often occurs in pain, fever, chronic/acute inflammation and cancer. The common intermediate in prostanoid production, PGH2, is produced from arachidonic acid by the cyclooxygenases (COXs). There are two cyclooxygenases, COX-1 and COX-2. COX-1 is usually expressed constitutively; COX-2 is induced by many stimuli. Non-steroidal anti-inflammatory drugs (NSAIDs) are analgesic, anti-pyretic and anti-inflammatory. They exert nearly all their biological actions by inhibiting COX activity. Discovery of COX-2 lead to development of the coxibs (e.g., Celebrex and Vioxx), which selectively inhibit COX-2. COX-2 expression - and prostaglandin production - is elevated in neurological degenerative diseases, in inflammatory conditions and in many cancers. Consequently, regulation of COX-2 expression is an extraordinarily active and important area of molecular, cellular and organismal research. We have created an heterozygous mouse in which the coding region of the firefly luciferase bioluminescence reporter gene has been "knock-into" one allele of the COX-2 gene at the ATG start site of translation. Thus one chromosome of this mouse expresses the COX-2 protein from one endogenous COX-2 regulatory regjon and the other chromosome expresses luciferase from the other endogenous COX-2 regulatory region. We will use this genetically modified mouse to non-invasively and repeatedly monitor COX-2 transcriptional activation in four inflammatory models (paw, air pouch, skin and lung) and in initiation, progression, metastasis and response to therapy of skin and colon cancer models. More recently it has become clear that regulation of COX-2 mRNA stability, modulated by the 3' untranslated region (3'UTR) of the COX-2 message, also plays a major role in regulating COX-2 levels in inflammatory responses and cancer. We will develop methods to non-invasively and repeatedly measure, in living mice, the effects of inflammatory stimuli and tumor initiation/progression on COX-2 mRNA stability. The ability to monitor, non-invasively and repeatedly, both COX-2 transcriptional activation and COX-2 mRNA stabilization will provide new insights into mechanisms of inflammation, tumor progression and neurological diseases as well as tools to monitor alternative therapies for these pathophysiologies. We will also create a transgenic mouse in which a fusion protein of the firefly luciferase optical imaging reporter and the HSVI-thymidine kinase PET reporter can be conditionally expressed as a result of Cre recombinase activation. Studies with this mouse will correlate optical and microPET imaging technologies.